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| United States Patent |
5,188,866
|
|
Yamamoto
, et al.
|
February 23, 1993
|
Process of making a magnetic recording medium
Abstract
The magnetic recording medium comprises a substrate, a recording coating of
a ferromagnetic metal and an aromatic organic polymer having a
weight-average molecular weight of 1,000 to 5,000,000. The magnetic
recording medium is produced by a plating method or a vaporization method
so as to form co-deposition of the metal and the polymer. The magnetic
recording medium produced is improved in resistance to corrosion.
| Inventors:
|
Yamamoto; Yuzo (Wakayama, JP);
Nomoto; Katsunori (Tochigi, JP);
Isobe; Tsutomu (Tochigi, JP)
|
| Assignee:
|
Kao Corporation (Tokyo, JP)
|
| Appl. No.:
|
791390 |
| Filed:
|
November 14, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
427/132; 427/250; 427/255.31; 427/255.38; 427/255.6; 427/443.1 |
| Intern'l Class: |
B05D 005/12 |
| Field of Search: |
427/128-132,48,250,255.2,255.6,443.1
428/694,695,900
|
References Cited
Attorney, Agent or Firm: Birch, Stewart, Kolasch & Birch
Parent Case Text
This application is a divisional of copending application Ser. No.
07/292,533, filed on Dec. 30, 1988, U.S. Pat. No. 5,080,982, now allowed,
the entire contents of which are hereby incorporated by reference.
Claims
We claim:
1. A process for preparing a magnetic recording medium which comprises a
substrate and a recording layer coated on the substrate comprising:
immersing a substrate into an aqueous solution comprising a ferromagnetic
metal ion, a reducing agent for the metal ion, a complexing agent for the
metal ion, a pH buffer, an adjuster and 0.005 to 100 g per liter of an
aromatic organic polymer (B') and
co-depositing and continuously forming onto the substrate, a thin film of a
ferromagnetic metal, and being contained in the film, 0.001 to 30 percent
by weight, based on the film, of an aromatic organic polymer (B') having a
weight-average molecular weight of 1,000 to 1,000,000 and comprising at
least one aromatic ring and 1 to 10 hydroxyl groups (--OH) on the average
based on 500 units of the molecular weight and further, as an
indispensable component, 0.1 to 4 sulfone groups (--SO.sub.3) or 0.1 to 6
groups on the average, based on 500 units of the molecular weight, of at
least one polar group selected from the group consisting of a phosphate
group represented by the formula
##STR83##
a phosphite group represented by the formula
##STR84##
a phosphonate group represented by the formula
##STR85##
a phosphonite group represented by the formula
##STR86##
a phosphinate group represented by the formula
##STR87##
a phosphinite group represented by the formula
##STR88##
a tertiary amino group represented by the formula
##STR89##
and a quaternary ammonium group represented by the formula
##STR90##
wherein R is a hydrogen atom or a hydrocarbon group, R.sub.1, R.sub.2,
and R.sub.3 which may be the same or different are each a straight-chain
group, a branched alkyl group, a hydroxyalkyl group or an aromatic group,
and X is a counter anion, a carboxyl group )--COOH), or a nitro group,
wherein said aromatic rings are linked to each other through a main chain
comprising at least one member selected from a C--C, C.dbd.C, or ether
(C--O--C) bond.
2. The process as claimed in claim 1, in which R.sub.1, R.sub.2 and R.sub.3
are each a phenyl group or a benzyl group.
3. The process as claimed in claim 1, in which the film contains 0.001 to
10 percent by weight of polymer (B').
4. The process as claimed in claim 1, in which the film contains 0.001 to
10 percent by weight of polymer (B').
5. The process as claimed in claim 1, in which polymer (B') is contained in
the crystal grain of the metal.
6. The process as claimed in claim 1, in which polymer (B') is soluble or
dispersible in water.
7. The process as claimed in claim 1, in which a metal is contained in the
molecule of polymer (B').
8. The process as claimed in claim 7, in which the metal is selected from
the group consisting of Co, Ni, Ti, Pd, Pt, Zr, Hf, Rh, Fe, V, Cr, Mo and
Si.
9. The process as claimed in claim 1, in which at least one of said hydroxy
group is attached to at least one of said aromatic ring.
10. The process as claimed in claim 1, which is conducted while controlling
proportions of polymer (B') to the entire codeposited thin film in a range
of 0.01 to 30 percent by weight, to affect an electroless plating.
11. A process for preparing a magnetic recording medium which comprises a
substrate and a recording layer coated on the substrate comprising:
co-depositing and continuously forming by evaporation onto the substrate, a
thin film of a ferromagnetic metal and being contained in the film, 0.001
to 10 percent by weight, based on the film of an aromatic organic polymer
(B') having a weight-average molecular weight of 1,000 to 1,000,000 and
comprising at least one aromatic ring and 1 to 10 hydroxyl groups (--OH)
on the average based on 500 units of the molecular weight and further, as
an indispensable component, 0.1 to 4 sulfone groups (--SO.sub.3) or 0.1 to
6 groups on the average, based on 500 units of the molecular weight, of at
least one polar group selected from the group consisting of a phosphate
group represented by the formula
##STR91##
a phosphite group represented by the formula
##STR92##
a phosphonate group represented by the formula
##STR93##
a phosphonite group represented by the formula
##STR94##
a phosphinate group represented by the formula
##STR95##
a phosphinite group represented by the formula
##STR96##
a tertiary amino group represented by the formula
##STR97##
and a quaternary ammonium group represented by the formula
##STR98##
wherein R is a hydrogen atom or a hydrocarbon group, R.sub.1, R.sub.2,
and R.sub.3 which may be the same or different are each a straight-chain
group, a branched alkyl group, a hydroxyalkyl group or an aromatic group,
and X is a counter anion, a carboxyl group (--COOH), or a nitro group,
wherein said aromatic rings are linked to each other through a main chain
comprising at least one member selected from a C--C, C.dbd.C, or ether
(C--O--C) bond.
12. The process as claimed in claim 11, which is conducted while
controlling proportions of polymer (B') to the entire co-deposited thin
film in a range of 0.01 to 30 percent by weight.
13. A process for preparing a magnetic recording medium which comprises a
substrate and a recording layer coated on the substrate comprising:
co-depositing and continuously forming by evaporation onto the substrate, a
thin film of a ferromagnetic metal and being contained in the film 0.001
to 10 percent by weight, based on the film, of an aromatic organic polymer
(A) defined by formula (A):
##STR99##
wherein m.gtoreq.0 and n.gtoreq.3 and each is an arbitrary number
necessary for said organic aromatic polymer defined by formula (A) to have
a weight-average molecular weight up to 1,000,000;
.gtoreq. k.gtoreq.2;
0.gtoreq.p.gtoreq.2;
provided that k+p+m.gtoreq.0;
R.sup.1, R.sup.2, and R.sup.3 are each H or an alkyl group having 1 to 5
carbon atoms;
X is a polymerizable vinyl monomer; and
Y and Z which may be the same or different are each selected from the group
consisting of
##STR100##
CR.sup.4 R.sup.5 OR.sup.6, --CH.sub.2 OH, an alkyl group having 1 to 18
carbon atoms and an aryl group, wherein M is H, an alkali metal, an
alkaline earth metal, or an organic cation of an amine;
Y.sup.1 and Y.sup.4 are each a halogen;
Y.sup.2 and Y.sup.3 are each a counter ion selected from a halogen ion, an
organic acid anion, or an inorganic acid anion;
W is S or O;
R.sup.4 to R.sup.8 which may be the same or different are each a
straight-chain group, a branched alkyl group, a hydroxyalkyl group, an
aromatic group, or H, provided that R.sup.6 R.sup.7 may be combined to
form a ring together with the N group;
R.sup.9 to R.sup.15 which may be the same or different are each a
straight-chain group, a branched alkyl group, a hydroxyalkyl group, an
aromatic group, or H;
q, s, and t are each 0 or 1; and
r is 0, 1, or 2.
14. The process as claimed in claim 13, which is conducted while
controlling proportions of polymer (A) to the entire co-deposited thin
film in a range of 0.01 to 30 percent by weight.
15. A process for preparing a magnetic recording medium which comprises a
substrate and a recording layer coated on the substrate comprising:
immersing a substrate into an aquesous solution comprising a ferromagnetic
metal ion, a reducing agent for the metal ion, a complexing agent for the
metal ion, a pH buffer, an adjuster and 0.005 to 100 g per liter of an
aromatic organic polymer (A) and
co-depositing and continuously forming onto the substrate, a thin film of a
ferromagnetic metal, and being contained in the film, 0.001 to 30 percent
by weight, based on the film, of an aromatic organic polymer (A) defined
by formula (A):
##STR101##
wherein m.gtoreq.0 and n.gtoreq.3 and each is an arbitrary number
necessary for said organic aromatic polymer defined by formula (A) to have
a weight-average molecular weight up to 1,000,000;
.ltoreq. k.ltoreq.2;
0.ltoreq.p.ltoreq.2;
provided that k+p+x.gtoreq.0;
R.sup.1, R.sup.2, and R.sup.3 are each H or an alkyl group having 1 to 5
carbon atoms;
x is a polymerizable vinyl monomer; and
Y and Z which may be the same or different are each selected from the group
consisting of
##STR102##
CR.sup.4 R.sup.5 OR.sup.6, --CH.sub.2 OH, an alkyl group having 1 to 18
carbon atoms and an aryl group, wherein M is H, an alkali metal, an
alkaline earth metal, or an organic cation of an amine;
Y.sup.1 and Y.sup.4 are each a halogen;
Y.sup.2 and Y.sup.3 are each a counter ion selected from a halogen ion, an
organic acid anion, or an inorganic acid anion;
W is S or O;
R.sup.4 to R.sup.8 which may be the same or different are each a
straight-chain group, a branched alkyl group, a hydroxyalkyl group, an
aromatic group, or H, provided that R.sup.6 and R.sup.7 may be combined to
form a ring together with the N group;
R.sup.9 and R.sup.15 which may be the same or different are each a
straight-chain group, a branched alkyl group, a hydroxyalkyl group, an
aromatic group, or H;
q, s, and t are each 0 or 1; and
r is 0, 1, or 2.
16. The process as claimed in claim 15, which is conducted while
controlling proportions of polymer (A) to the entire codeposited thin film
in a range of 0.01 to 30 percent by weight, to affect an electroless
plating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording medium such as
magnetic tape and a magnetic disk and a process for the preparation
thereof. The magnetic recording medium of the present invention is
improved in view of its durability and resistance to corrosion in addition
to its excellent recording properties.
2. (Prior Art)
In the state of arts, a magnetic recording medium is produced, for example,
by a physical method such as evaporation in vacuum and spattering, or a
chemical method such as electroless plating, on a substrate of glass or a
polymer containing a ferromagnetic metal or an alloy thereof. See for
example Japanese patent publication A No. 52-153 407 and 58-3963. It is to
be mentioned, however, that the prior medium is characterized with poor
durability and resistance to corrosion, although this characterization
effectively applies to high density recordings. The prior medium has a
large friction against a magnetic head and is easily abrased and
scratched. Moreover, it is not flexible and is therefor, instable during
operation, in view of its contact with the magnetic head. It is easily
corroded in air and as a result its magnetic properties, such as a
saturated density of magnetic flux, are reduced. Therefore,
The present invention overcomes the above discussed defects, in particular
provides an improvement in resistance to corrosion. This is attained by
use of a specific organic polymer together with deposition of a
ferromagnetic metal. It is preferable that the polymer is contained in the
matrix of the metal in the form of their complex.
SUMMARY OF THE INVENTION
The present invention provides a magnetic recording medium which comprises
a substrate and a recording layer, coated on the substrate, said recording
layer comprising a continuously formed thin film comprising a
ferromagnetic metal and 0.001 to 30 percent by weight, based on the film,
of an aromatic organic polymer having a weight-average molecular weight of
1,000 to 5,000,000, the polymer being contained in the film.
It is preferable that the recording film layer contains 0.01 to 30 percent
by weight of the polymer the polymer having a weight-averaqe molecular
weight of 1,000 to 1,000,000. The polymer is preferably soluble or
dispersible in water, and may be in the form of a micelle.
It is also preferred that the film contains 0.001 to 10 percent by weight
of the polymer, in particular when it is produced by the evaporation
method.
It is desirable that the polymer is contained within the crystal grain of
the deposited metal.
It is preferable that the polymer contains a metal in its molecule.
The metal contained in the polymer to be deposited on the substrate, is
preferably selected from the group consisting of Co, Ni, Ti, Pd, Pt, Zr,
Hf, Rh, Fe, V, Cr, Mo and Si.
The polymer preferably has at least one hydroxy group attached to its
aromatic ring.
The polymer preferably includes polymers (B), (B') and (A).
Polymer (B) has a weight-average molecular weight of 1,000 to 5,000,000 and
comprises at least one aromatic ring and 1 to 10 OH groups on the average,
based on 500 units of the molecular weight and further, as an
indispensable component, zero to 4 sulfone groups (--SO.sub.3) or zero to
6 groups on the average, based on 500 units of the molecular weight, of at
least one polar group selected from the group (a) consisting of a
phosphate group represented by the formula
##STR1##
a phosphite group represented by the formula a phosphonate group
represented by the formula
##STR2##
a phosphonite group represented by the formula
##STR3##
a phosphinate group represented by the formula
##STR4##
a phosphinite group represented by the formula
##STR5##
a tertiary amino group represented by the formula
##STR6##
and a quaternary ammonium group represented by the formula
##STR7##
, wherein R is hydrogen atom or a hydrocarbon group, R.sub.1, R.sub.2, and
R.sub.3 which may be the same or different are each a straight-chain or
branched alkyl or hydroxyalkyl group or an aromatic group, such as a
phenyl group or a benzyl group, and X is a counter anion; a carboxyl group
(--COOH) and a nitro group.
Polymer (B') has a weight-average molecular weight of 1,000 to 1,000,000
and comprises at least one aromatic ring and 1 to 10 OH groups on the
average based on 500 units of the molecular weight and further, as an
indispensable component, 0.1 to 4 sulfone groups (--SO.sub.3) or 0.1 to 6
groups on the average, based on 500 units of the molecular weight, of at
least one polar group selected from the group (a) consisting of a
phosphate group represented by the formula
##STR8##
a phosphite group represented by the formula a phosphonate group
represented by the formula
##STR9##
a phosphonite group represented by the formula
##STR10##
a phosphinate group represented by the formula
##STR11##
a phosphinite group represented by the formula
##STR12##
a tertiary amino group represented by the formula
##STR13##
and a quaternary ammonium group represented by the formula
##STR14##
wherein R is a hydrogen atom or a hydrocarbon group, R.sub.1, R.sub.2, and
R.sub.3 which may be the same or different are each a straight-chain or
branched alkyl or hydroxyalkyl group or an aromatic group, such as a
phenyl group or a benzyl group, and X is a counter anion; and a carboxyl
group (--COOH), wherein said aromatic rings are linked to each other
through a main chain comprising at least one member selected from the
group consisting of C--C, C.dbd.C, and ether (C--O--C) bonds.
Polymer (A) is defined by formula (A):
##STR15##
wherein m.gtoreq.0 and n.gtoreq.3 and each is an arbitrary number
necessary for said organic polymer represented by the general formula (A)
to have a weight-average molecular weight up to 1,000,000;
0.ltoreq.k.ltoreq.2;
0.ltoreq.p.ltoreq.2;
provided that k+p++m.gtoreq.0;
R.sup.1 to R.sup.3 are each H or an alkyl group having 1 to 5 carbon atoms;
X is a polymerizable vinyl monomer; and
Y and Z which may be the same or different are each selected from amoung
##STR16##
CR.sup.4 R.sup.5 OR.sup.6, --CH.sub.2 OH, alkyl groups each having 1 to 18
carbon atoms and aryl groups, wherein M is H, an alkali metal, an alkaline
earth metal, or an organic cation of an amine etc.;
Y.sup.1 and Y.sup.4 are each a halogen;
Y.sup.2 and Y.sup.3 are each a counter ion such as a halogen ion, an
organic acid anion, or an inorganic acid anion;
W is S or 0;
R.sup.4 to R.sup.8 which may be the same or different are each a
straight-chain or branched alkyl group, an alkyl group derivative such as
a hydroxyalkyl group, an aromatic group, or H, provided that R.sup.6 and
R.sup.7 may be combined to form a ring together with the N group;
R.sup.9 to R.sup.15 which may be the same or different are each a
straight-chain or branched alkyl group, an alkyl group derivative such as
a hydroxyalkyl group, an aromatic group, or H;
q, s, and t are each 0 or 1; and
r is 0, 1, or 2.
The magnetic recording medium of the invention can be produced, in general,
by the wet method and the evaporation method.
The wet method comprises the steps of immersing a base substrate to plate
into an aqueous solution containing a ferromagnetic metal ion, a reducing
agent for the metal ion, a complexing agent for the metal ion, a pH
buffer, an adjustor and 0.005 to 100 g per liter of the polymer as defined
above and co-depositing the metal and the polymer on the substrate,
preferably while controlling proportions of the polymer to the entire
co-deposited product in the range of 0.01 to 30 percent by weight, to
effect the electroless plating.
The evaporation method comprises the step of evaporating and co-depositing
on a substrate a ferromagnetic metal and the polymer defined above
concurrently, preferably while controlling proportions of the polymer to
the entire co-deposited product in the range between 0.001 to 10 percent
by weight.
In the present invention, the particle diameter and the shape of coated
crystals can be controlled by selecting fundamental skeletons (aromatic
rings and hydroxyl groups), types of a polar groups (sulfone groups or the
like), effect of the molecular weight (1,000 to 5,000,000) and amount of
addition (0.005 to 100 g/l) to be contained in the plating bath of the
organic polymer and by selecting the depositing conditions. Moreover the
present invention is also improved in corrosion resistance by the function
of the organic polymer in the form of a composite material (molecular
composite) prepared from a suitable amount of a specified polymer and a
metal.
Polymer (B) to be use in the present invention includes two, groups (a) and
(b). Group (a) includes a polymer having a weight-average molecular weight
of 1,000 to 5,000,000 and comprising, as indispensable components, at
least one aromatic ring, 1 to 10 hydroxyl groups on the average and zero
to 4 sulfone groups on the average each based on 500 units of the
molecular weight Examples of the polymer belonging to group (b) include an
anionic water-soluble organic polymer having a weight-average molecular
weight of 1,000 to 5,000,000 and comprising at least one aromatic ring
having at least one hydroxyl group as a substituent
##STR17##
and zero to 4 sulfone groups each based on 500 units of the molecular
weight.
The concept of the C--C, C.dbd.C, or ether (C--O--C) bond linking an
aromatic ring to another aromatic ring includes poly-p-hydroxystyrene,
sodium ligninsulfonate and nitrohumic acid. In the present invention, a
condensed ring
##STR18##
is not regarded as the above-described bond present in the main chain.
The water-soluble organic polymers belonging to the above-described groups
(a) and (b) may contain, in their side chain, functional groups other than
those described above, e.g., halogen groups, such as Cl and Br, and
nitrile, nitro and ester groups.
Examples of the water-soluble organic polymer meeting the requirements of
the groups (a) and (b) include the following compounds A-1 to A-11.
A-1: a phenol-formaldehyde resin (a novolak resin), a phenol-furfural
resin, a resorcinolformaldehyde resin, a sulfonate of each of the above
resin and a derivative of each of the above resin.
A-Z: epoxy resins such as an epoxy resin having a bisphenol A group,
epoxyacrylate and phenol(EO).sub.5 glycidylether and a sulfonate of each
epoxy resin, and a condensate with formalin of bisphenol A or its sodium
sulfonate or bisphenol S or its sodium sulfonate.
A-3: a sulfonate of polyhydroxyvinylpyridine.
A-4: a salt of a condensate of formalin with a sulfated creosote oil, a
salt of condensate of formalin with an alkylphenol, its derivative or its
sulfonation product, including a m-cresolmethylenesulfonic acid-formalin
condensate, a condensate of formalin with sodium
m-cresol-bakelitemethylenesulfonate and Schaeffer's acid and a condensate
of formalin with 2-(2'-hydroxyphenyl)-2-(2'-hydroxy)-sulfomethylpropane,
or a salt of a condensate of formalin with a phenol, a phenolic carboxylic
acid or their sulfonation product. Examples of the phenols include phenol,
o-cresol, m-cresol, p-cresol, 3,5-xylenol, carvacrol, thymol, catechol,
resorcinol, hydroquinone, pyrogallol, and phloroglucinol.
Examples of the phenolic carboxylic acid include salicylic acid,
m-hydroxybenzoic acid, p-hydroxybenzoic acid, protocatechuic acid,
gentisic acid, .alpha.-resorcylic acid, .beta.-resorcylic acid,
.gamma.-resorcylic acid, orsellinic acid, caffeic acid, umbellic acid,
gallic acid, and 3-hydroxyphthalic acid.
A-5: a condensate of formalin with mono- or poly-hydroxynaphthalene, its
derivative or a sulfonation product thereof.
Examples of the monohydroxynaphthalene include .alpha.-naphthol and
.beta.-naphthol. Examples of the polyhydroxynaphthalene include
.alpha.-naphthohydroquinone (1,4-dihydroxynaphthalene),
.beta.-naphthohydroquinone (1,2-dihydroxynaphthalene), naphthopyrogallol
(1,2,3-trihydroxynaphthalene), and naphthoresorcinol
(1,3-dihydroxynaphthalene).
A-6: a condensate of formalin with phenylphenolsulfonate.
A 7: a condensate of formalin with dihydroxydiphenyl or its sulfonation
product; and a formalin condensate of bishydrbxyphenyl naphthalene, a
condensate of formalin with bis(hydroxyphenyl) sulfone
naphthalenesulfonate, a condensate of formalin with bis(hydroxydiphenyl)
sulfone monomethylsulfonate, and a condensate of formalin with
hydroxydiphenyl sulfone monosulfonate.
A-8: a polyhydroxystyrene derivative or its sulfonate such as
poly-p-hydroxystyrene, brominated poly-p-hydroxystyrene,
poly-p-hydroxymethoxystyrene, and poly-p-hydroxydimethoxystyrene.
A-9: ligninsulfonic acid or salt thereof, which is a compound prepared by
treating a pulp mill waste liquor produced as a by-product by various
processes and mainly composed of ligninsulfonic acid or salt thereof.
Lignin has a chemical structure comprising a three-dimensional structure
composed of a phenylpropane group as the basic skeleton.
With respect to ligninsulfonic acid and salt thereof, various types of
products are manufactured and sold by various pulp manufacturers. The
molecular weight of the products ranges from 180 to 1,000,000, and the
products are available in various types, i.e., have various degrees of
sulfonation, are in various salts form and chemically modified form, and
contain varied heavy metal ions. All of these types of ligninsulfonic acid
and salts thereof are not always useful for attaining the object of the
present invention. The effect greatly varies depending upon the types. The
object of the present invention can be most effectively attained when a
particular ligninsulfonic acid and salt thereof are used. That is, there
is a limitation to preferable ligninsulfonic acid and salt thereof which
may be used in the present invention. In particular, ligninsulfonic acid
and its salt of the present invention is preferred in meeting a
requirement that none of these compounds used has a molecular weight of
less than 1,000, or if any, only a few would.
There is no particular limitation on the types of ligninsulfonates used in
the present invention, and any of sodium, potassium, calcium, ammonium,
chromium, iron, aluminum, manganese, and magnesium salts may be used.
A ligninsulfonic acid and salts thereof which have been chelated with heavy
metal ions, such as Fe, Cr, Mn, Mg, Zn or Al ions, may also be used in the
present invention.
Further, a ligninsulfonic acid and salts thereof, to which other organic
compounds, such as naphthalene or phenol, or organic polymers have been
added, may also be used. The ligninsulfonic acid and salts thereof used in
the present invention may contain impurities derived from the manufacture
of pulp. However, the smaller the amount of the impurities, the better the
effect of the compound.
A 10: polytannic acid, its derivative and its sulfonation product.
A-11: a sulfonation product of humic acid or nitrated humic acid and a
derivative thereof or a salt thereof.
The organic polymer includes the following examples (c) and (d).
Group (c): an anionic, cationic or amphoteric, water-soluble organic
polymer having a weight-average molecular weight of 1,000 to 5,000,000 and
comprising at least one aromatic ring and 1 to 10 hydroxyl groups on the
average and further, as an indispensable component, based on 500 units of
the molecular weight, zero to 4 sulfone groups (--SO.sub.3) or zero to 5
groups on the average of at least one polar group selected from the group
(a) consisting of a phosphate group represented by the formula
##STR19##
a phosphite group represented by the formula a phosphonate group
represented by the formula
##STR20##
a phosphonite group represented substituent, at least one hydroxyl group
based on 500 units of the molecular weight and further, as an
indispensable component, based on 500 units of the molecular weight, zero
to 4 sulfone groups (--SO.sub.3) or zero to 5 groups on the average of at
least one polar group selected from the group (a) consisting of a
phosphate group represented by the formula
##STR21##
a phosphorite group represented by the formula
##STR22##
a phosphonate group represented by the formula
##STR23##
a phosphonite group represented by the formula
##STR24##
a phosphinate group represented by the formula
##STR25##
a phosphinite group represented by the formula
##STR26##
a tertiary amino group represented by the formula
##STR27##
by the formula a phosphinate group represented by the formula
##STR28##
a phosphinite group represented by the formula
##STR29##
a tertiary amino group represented by the formula
##STR30##
and a quaternary ammonium group represented by the formula
##STR31##
wherein R is a hydrogen atom or a hydrocarbon group, R.sub.1, R.sub.2, and
R.sub.3 which may be the same or different are each a straight-chain or
branched alkyl or hydroxyalkyl group or an aromatic group, such as a
phenyl group or a benzyl group, and X is a counter anion, carboxyl group
and nitro group.
Group (d): an anionic, nonionic, cationic or amphoteric, organic polymer
having a weight-average molecular weight of 1,000 to 5,000,000 and
comprising at least one aromatic ring having, as a a quaternary ammonium
group represented by the formula
##STR32##
wherein R.sub.1, R.sub.2, and R.sub.3 which may be the same or different
are each a straight-chain or branched alkyl or hydroxyalkyl group or an
aromatic group, such as a phenyl group or a benzyl group, and X is a
counter anion.
The organic polymer having the groups (c) and (d) may also have on its side
chain, functional group(s), other than the polar groups shown above, such
as halogen e.g., Cl or Bl, and nitril, nitro and ester.
The polymer having the groups (c) and (d) includes the following compounds
B-1 to B-4.
B-1: an anionic or amphoteric, organic polymer, prepared by introducing at
least one polar group selected from among those of the following group
(I), onto a base polymer composed of the above-described organic polymers
A-1 to A-11:
polar groups of group (I): tertiary amino, the above-described group (I)
into a starting material composed of the above-described polymers A-4' to
A-7'.
B-2: a copolymer of poly-p-vinylhydroxystyrene with maleic anhydride; and a
product of amination or phosphorylation of the copolymer.
B-3: a sulfonation product of a condensate of formalin with
phenylphosphonic acid and a derivative thereof and phenol and a derivative
thereof or resorcinol or a derivative thereof; and a salt thereof.
Examples of the derivative of phenylphosphonic acid include monooctyl
phenylphosphonate, diphenylphosphonic acid, 0-methyl hydrogen
phenylthiophosphoate, and diphenylphosphinic acid.
Examples of the derivative of resorcinol include 2,6-dihydroxyacetophenone,
2,4-dihydroxyacetophenone, resorcinol monomethyl ether, resorcinol
monohydroxyethyl ether, 2-methylresorcinol, 7-hydroxy-4-methylcoumarin,
and 2-ethylresorcinol.
Examples of phenol include all of the phenols, phenolic carboxylic acids
and alkylphenols described above with respect to compound A-4.
B-4: humic acid, nitrohumic acid and salts thereof or amination products of
these humic acids.
It is also possible to select at least one member from among the compounds
of the above-described quaternary ammonium base, carboxyl, phosphate,
phosphite, phosphonate, phosphonite, phosphinate, and phosphinite groups;
or
an anionic, cationic or amphoteric and waterorganic polymer prepared by
introducing at least one polar group selected from among those of the
above-described group (I) into a starting material composed of an organic
polymer before sulfonation in the organnic polymers A-1, A-2, A-3, A-4,
A-8, A-9, A-10, and A-11; or
a compound prepared by modifying the following starting material composed
of the formalin condensate A-4, A-5, A-6, or A-7 which is free of the
sulfone group:
A-4': a condensate of formalin with phenol, a phenolic carboxylic acid, or
an alkylphenol and a derivative thereof,
A-5': a condensate of formalin with mono- or polyhydroxynaphthalene and a
derivative thereof,
A-6': a condensate of formalin with phenylphenol,
A-7'a condensate of formalin with dihydroxydiphenyl, or the like,
i.e., an anionic, cationic or amphoteric, waterorganic polymer prepared by
introducing at least one polar group selected from among those of A or B
or both of the above-described groups A and B and use them in the form of
a mixture. There is no limitation as to the type of the salt of organic
polymer, and sodium, calcium and ammonium salts, etc., may be used.
Further, examples of the organic polymer of hydroxystyrene, which may be
used in the present invention, include a-water-soluble organic polymer
having a weight-average molecular weight of 1,000 to 5,000,000 and
comprising, as an indispensable component, based on 500 units of the
molecular weight, at least 0.5 aromatic ring having at least one hydroxyl
group (--OH).
The above-described organic polymer may contain, in its side chain,
functional groups other than those described above, e.g., halogen groups,
such as Cl and Br, and nitrile, nitro and ester groups.
The present inventors have found that a magnetic coating having excellent
corrosion resistance can be prepared by the use of an additive for a
plating bath comprising, among the above-described organic polymers, a
water-soluble organic polymer represented by the following general formula
(A):
##STR33##
wherein m.gtoreq.0 and n.gtoreq.3 and each is an arbitrary number
necessary for said organic polymer represented by the general formula (A)
to have a weight average molecular weight up to 1,000,000;
0.ltoreq.k.ltoreq.2;
0.ltoreq.p.ltoreq.2;
provided that k+p+m.gtoreq.0;
R.sup.1 to R.sup.3 are each H or an alkyl group having 1 to 5 carbon atoms;
X is a polymerizable vinyl monomer; and
Y and Z which may be the same or different are each selected from among
##STR34##
alkyl groups each having 1 to 18 carbon atoms and aryl groups, wherein M
is H, an alkali metal, an alkaline earth metal, or an organic cation of an
amine ets.;
Y.sup.1 and Y.sup.4 are each a halogen;
Y.sup.2 .crclbar. and Y.sup.3 .crclbar. are each a counter ion such as a
halogen ion, an organic acid anion, or an inorganic acid anion;
W is S or 0;
R.sup.4 to R.sup.8 which may be the same or different are each a
straight-chain or branched alkyl group, an alkyl group derivative such as
a hydroxyalkyl group, an aromatic group, or H, provided that R.sup.4 and
R.sup.7 may be combined to form a ring together with the N group;
R.sup.9 to R.sup.15 which may be the same or different are each a
straight-chain or branched alkyl group, an alkyl group derivative such as
a hydroxyalkyl group, an aromatic group, or H;
q, s, and t are each 0 or 1; and
r is 0, 1, or 2.
In the above-described general formula (A), m, n, k, and p are each not
limited to an integer and may be any number (a real number) in a
particular range. On the level of a monomer constituting a polymer, it is
a matter of course that k and p are each an integer. On the level of a
constituent block unit, m is an integer, while on the level of a molecule,
n is an integer. However, a polymer is essentially a mixture, and it is
more proper to regard the property of the mixture as the property of the
polymer than to judge the property of the polymer from that of the
individual constituent unit. Therefore, in the present invention the
general formula (A) represents an average composition.
The organic polymer of hydroxystyrene represented by the general formula
(A) may be a homopolymer of a monomer having or is free from a substituent
represented by Y or Z in the general formula (A), such as hydroxystyrene,
isopropenylphenol (hydroxy-.alpha.-methylstyrene) or
hydroxy-.alpha.-ethylstyrene, a copolymer of the monomers thereof, or a
copolymer of the above-described hydroxystyrene monomer with other
polymerizable vinyl monomer (X). Hydroxystyrene, isopropenylphenol, or the
like, which is a polymer unit may be an ortho, meta or para isomer or a
mixture of these units, among which a para or meta isomer is preferable.
With respect to the above-described copolymer, examples of the other vinyl
monomer include maleic anhydride, maleic acid, acrylic acid, methyl
methacrylate, methacrylic acid, glycidyl methacrylate, hydroxyethyl
methacrylate, itaconic acid, allylsulfonic acid, styrenesulfonic acid,
ethyl acrylate phosphate, acrylamide, 2-acrylamido-2-methylpropanesulfonic
acid, acrylonitrile, maleimide, vinylpyridine, acrylic ester, methacrylic
ester, fumaric ester or vinyl esters of various organic acids. In this
case, the molar ratio of the hydroxystyrene compound unit, such as
hydroxystyrene or isopropenylphenol unit, to the other vinyl monomer is
preferably 1/10 to 20/1. Suitable examples of the alkali metal or alkaline
earth metal M in the substituent of the hydroxystyrene unit, i.e.,
##STR35##
include Li, Na, K, Mg, Ca, Sr, and Ba. The introduction of the sulfone
group can be attained by an ordinary sulfonation process in which fuming
sulfuric acid, sulfuric anhydride, or the like is used as a sulfonating
agent. R.sup.4 to R.sup.8 in the substituent
##STR36##
which may be the same or different is selected from among a straight-chain
or branched alkyl group having 1 to 36 carbon atoms, an alkyl derivative
group such as a hydroxyalkyl, aminoalkyl, phosphoalkyl or mercaptoalkyl
group, and an aromatic group such as a benzyl group substituted with a
straight-chain or branched alkyl group having 1 to 16 carbon atoms.
R.sup.6 and R.sup.7 may be combined to form a ring. Therefore, preferable
examples of R.sup.4 to R.sup.8 include a straight-chain or branched alkyl
group, a hydroxyalkyl group, or an aromatic group substituted with a
straight-chain or branched alkyl group having 1 to 5 carbon atoms. With
respect to the introduction of the above-described tertiary amino group,
##STR37##
can easily be prepared by, e.g., the Mannich reaction in which a
dialkylamine and formaldehyde are employed.
An organic or inorganic acid for neutralizing the amino moiety may be used
in order to improve the water-solubility. Examples of the acid useful for
this purpose include acetic acid, citric acid, oxalic acid, ascorbic acid,
phenylsulfonic acid, chloromethylphosphonic acid, monochloroacetic acid,
dichloroacetic acid, trichloroacetic acid, trifuloroacetic acid, sulfuric
acid, phosphoric acid, hydrochloric acid, boric acid, nitric acid,
hydrofluoric acid, hexafluorosilisic acid, hexafluorotitanic acid, and
hexafluorozirconic acid. These acids may be used either alone or in the
form of a mixture.
With respect to the introduction of the quaternary ammonium base,
##STR38##
can easily be prepared by, e.g., the Menshutkin reaction which is a
reaction of the above-described tertiary amine compound with an alkyl
halide.
R.sup.9 to R.sup.15 in the following substituents of the hydroxystyrene
unit:
##STR39##
which may be the same or different are selected from among a
straight-chain or branched alkyl group having 1 to 36 carbon atoms, an
alkyl derivative group such as a hydroxyalkyl, aminoalkyl, mercaptoalkyl
or phosphoalkyl group, and an aromatic group such as a phenyl group
substituted with a straight-chain or branched alkyl group having 1 to 16
carbon atoms, provided that the carbon chain has such a length as will
cause the water-solubility of the above-described compound (A) to
disappear. In view of the above, preferable examples of R.sup.9 to
R.sup.15 include a straight-chain or branched alkyl or hydroxyalkyl group
having 1 to 8 carbon atoms, or an aromatic group substituted with a
straight-chain or branched alkyl group having 1 to 5 carbon atoms. The
hydroxystyrene polymer represented by the formula (D) can be prepared by,
e.g., a process described in Japanese Patent Laid-Open No. 47489/1978,
i.e., by halogenating or halomethylating a hydroxystyrene polymer,
reacting the product with a trivalent phosphorus compound (Arbuzov
reaction), and subjecting the reaction product to thermal rearrangement.
The hydroxystyrene polymer represented by the formula (C) can be prepared
by, e.g., a process described in Japanese Patent Laid-Open No. 71190/1978,
i.e., by hydroxymethylating a hydroxystyrene polymer and reacting the
product with a reagent for introducing a phosphoric acid or ester group. A
hydroxystyrene polymer substituted by a phosphonium group represented by
the formula
##STR40##
can easily be prepared by, e.g., a process described in Japanese Patent
Laid-Open No. 34444/1986, i.e., by reacting a hydrogen halide and
formaldehyde with a hydroxystyrene polymer to effect halogenomethylation
(e.g., chloromethylation) and then reacting a trivalent phosphite with the
product. The hydroxystyrene polymer may be one prepared by any process,
and it does not matter how the polymer has been prepared. For example,
poly-p-hydroxystyrene which is a polyhydroxystyrene homopolymer can easily
be prepared by cationic, radical, organic acid, or thermal polymerization
of p-hydroxystyrene. The organic acid polymerization products a polymer
having a weight-average molecular weight of tens of thousands to hundreds
of thousands, the thermal polymerization produces a polymer having a
weight-average molecular weight of thousands to tens of thousands, and the
radical polymerization of p-acetoxystyrene followed by hydrolysis produces
poly-p-hydroxystyrene having a weight average molecular weight of tens of
thousands to 2,000,000.
The organic polymer preferably includes one of groups (a) and (b), which
have all or part of hydroxyl group(s) attached on the aromatic ring(s).
The polymer (A) is most preferable. The polymer having a hydroxyl group is
attached to the aromatic ring thereof, could be easily dispersed into the
metal crystal, forming a complex therewith, which improve its resistance
to corrosion. The complex between the metal and the polymer (A) has a
smaller inside stress and is improved also in its adhesion to a substrate.
A polymer having a metal in its molecular chain which may be used in the
present invention, includes groups (i) and (ii) listed below.
(i) polymer having a metal in its main chain
##STR41##
In the formulae listed above, R is an alkyl, Ph is phenyl, M is one of Co,
Ni, Ti, Pd, Pt, Zr, Hf, Rh, Fe, V, Cr, Mo and Si, X is oxygen, nitrogen or
sulfur, n is a natural number being larger than 5, 1 is a natural number,
and m is an integer being not less than 1.
In addition to the metal-containing organic polymer shown above, the group
(i) also includes organic polymers defined by the groups (a) to (d) and
then containing a metal in their main chain.
(ii) a polymer having a metal in its side chain
##STR42##
In the formulae, R, Ph, M, n and 1 are defined above in the groups (i) and
X1 is one of Cl, Br, CN, Ph and CO3. m is an integer of 1 to 20. In the
above shown polymers, the group (ii) further includes polymers defined by
the groups (a) to (d) and containing a metal in their side chains.
( BRIEF DESCRIPTION OF DRAWINGS)
FIG. 1(a), (b) and (d) show the co-deposition of grains of metal crystals
and polymer particles and on the other hand FIG. 1 (c) shows the prior
magnetic material to the same effect. FIG. 2 shows pictures of SEM
(scanning electron microscope) on the surface of a magnetic layer of Co
and Ni in FIG. 2(a), shown in Comparative Example 104, and the surface of
a complex magnetic layer of Co, Ni and a polymer in FIG. (b), shown in
Example 76. It is seen that the grains of the metal crystal become a
little smaller with a complex with the polymer and then more round. The
polymer is not seen to have been maldistributed. FIG. 3(a) and (b), FIG.
4(a) and (b) and FIG. 5(a) and (b) show pictures of TEM on super-thin
slices of the magnetic films obtained in Examples 76, 80 and 79,
respectively, on the part of (b) and then illustrate them in (a). In the
phase-contrast method, the pictures show the co-deposited polymer which is
seen in the form of rods or dots and has a particle size of about 50 to
100 A, being of the molecular order, well dispersed and complexed with the
metal. The metal is found to have a crystal size of about 500 A.
The reason why the organometallic polymer is used is for improving the
decomposition stability at the time of physical vapor deposition when an
organic polymer is introduced into a metal element, and for improving the
resistance to corrosion of the magnetic film that will occur due to the
chemical and electrochemical properties of the metal element. The present
inventors have found that the action of hydroxyl groups and polar groups
can improve the corrosion resistance, and that when an aromatic organic
polymer is used in the composite material, different metal elements can be
made into a composite relatively easy in a microscopic fashion, and
excellent corrosion resistance due to the interaction between the polymer
and the contained metal can be realized. As one of the features of the
case using the organometallic polymer it can be mentioned that the effect
of improving corrosion resistance is recognized with the codeposited
amount smaller than that of the case wherein a polymer free from a metal
element is co-deposited.
In the method for the production of the present invention, there are two
major features: a first feature is that an organic polymer and a magnetic
metal are made into a composite (are made into a molecular composite) on a
molecular level (in the order of molecules), and an organic polymer is
co-deposited at the grain boundaries (i.e., between the grains) and in the
grains of the metal or only in the grains of the metal thereby making the
organic polymer into a composite; and a second feature is that only a
small amount (0.001 to 10 wt. %) of an organic polymer is made into a
composite to improve the corrosion resistance.
One example of the film structure of the present invention having such a
significant feature is that it takes a co-deposition pattern of the model
drawing a, b or d of FIG. 1. They are hereinafter referred to generally as
a molecular composite film. In the type as shown by the pattern C wherein
an organic polymer flocculates and segregates only at the grain
boundaries, an improvement of corrosion resistance as intended by the
present invention cannot be attained. The reason for this is considered to
be as follows; thus, it is known that corrosion of a metal generally
starts at grain boundaries and progresses along the boundaries, and the
diffusion of H.sub.2 O, and O.sub.2 that are essential components for a
corrosion reaction is higher in an organic polymer than in a metal;
therefore, it is considered that the co-deposited state of the pattern C
facilitates the diffusion of corrosive components, and not only cancels
the effect of a specified organic polymer of suppressing corrosion, but
also facilitates a corrosion reaction.
By attaining this molecular composite structure, for the first time the
formation of a composite of an organic polymer can be realized without
influencing adversely the magnetic properties of magnetic metal crystals.
In the present invention, it has been found that the chemical structure of
an organic polymer to be used has a quite important action in the
attainment of the molecular composite film structure that acts an
important role in the present invention.
The ferromagnetic film used in the present invention refers to Co, Fe, Ni
or Cr or an alloy, using it as a base such as Co--Ni, Co--Fe, Co--Cr,
Co--Cu, Co--Pt, Co--Cd, Co--Sn, Co--Ni--Cr and their oxides, and may
include an in-plane magnetized film and a perpendicularly magnetized film
according the magnetizing method.
The organic polymers that can be used in the present invention are limited
to those having a weight-average molecular weight in the range of 1,000 to
5,000,000, preferably 1,000 to 1,000,000. This is because the molecular
weight of the organic polymer affects the effect of the present invention,
and if the polymer has a molecular weight of less than 1,000, it is liable
to decompose during the physical vapor deposition, and the effect of
improving corrosion resistance is hardly secured, while if the polymer has
a molecular weight of more than 5,000,000, the physical vapor deposition
becomes difficult or it dissolves or disperses poorly in a plating bath,
which causes such a problem that the concentration thereof in the plating
bath is limited, and at the same time the effect of the present invention
is hardly secured. When organic polymers are to be charged into a plating
bath, it is better to use an organic polymer having a rather smaller
molecular weight because it will be easily attained to dissolve and
disperse it stably although the amount of the organic polymer that will
dissolve depends on the pH of the bath, the concentration of the salts
involved, the density of the polar groups of the polymer, and so on.
Further if the organic polymer has a rather smaller molecular weight, a
uniform polymer composite film is easily obtained. In contrast, if a film
is formed by physical vapor deposition, the upper limit of the molecular
weight of organic polymers is not too restricted in comparison with the
case of the plating method, and when the organic polymer has a rather
higher molecular weight, the magnetic properties are hardly disturbed, and
good results are liable to be obtained.
Polar groups (excluding hydroxyl groups and aromatic rings) such as sulfone
groups and phosphoric acid groups are important because they provide
corrosion resistance and solubility of the organic polymer into the
plating bath, and the preferable range of the density of polar groups is
0.1 to 5 groups, more preferably 1 to 3 groups, per a molecular weight of
500, on average. If the density of polar groups is less than 0.1 group, it
causes a problem that it dissolves in the plating bath poorly, while if
the density of polar groups exceeds 5 groups, it causes such a problem
that the corrosion resistance of the deposit film lowers. However, if a
physical vapor deposition method is used, it is preferable that there are
these polar groups, but they are not required necessarily.
The presence of hydroxyl groups is quite important in the present
invention. The action is not necessarily clarified, but it seems that
hydroxyl groups have various actions. For instance, it seems that they
have such actions that they influence the adsorption and reactivity of the
polymer onto the metal matrix, and that they densify and stabilize
corrosion products thereby improving corrosion resistance. It is
preferable that hydroxyl groups are bonded as substituents directly to the
aromatic rings because their effects are exhibited well. The main chain
connecting the aromatic rings is most preferably composed of C--C bonds
and C.dbd.C bonds free from a hetero atom, and C--O--C bonds are more
preferable to constitute the main chain connecting the aromatic rings
because of the stability to decomposition during the physical vapor
deposition and because of the stability to decomposition under a corrosive
environment.
The above factors such as the molecular weight, the constitutional unit,
the type and the density of polar groups, and the type of the main chain
of organic polymers are important factors for the additive of the present
invention and play essential roles.
In carrying out the present invention, the amount of the organic polymer to
be added to a plating bath is in the range of 0.005 to 100 g/l, preferably
0.01 to 20 g/l. If the amount of the organic polymer to be added is less
than 0.005 g/l, the effect is not observed, while the amount exceeds 100
g/l, the deposit film becomes brittle, causing a practical problem. In the
present invention, although the addition of one organic polymer exhibits
its effects, several organic polymers may be combined to be used.
The content of the organic polymer in the deposited film is in the range of
0.001 to 10 wt. %, preferably 0.01 to 1 wt. %, and most preferably 0.05 to
0.5 wt. %, based on the total weight of the deposited film. If the
co-deposited amount of the organic polymer is small, the corrosion
preventive effect is hardly exhibited because the film is brought nearly
to a simple metal deposit, while if the co-deposited amount is too
excessive, the deposited film becomes brittle, causing a practical
problem. The assessment of the brittleness can be easily found by
subjecting a sample deposited on a PET film substrate to a tensile test,
and measuring the elongation of the deposited film at the point where the
electroconductivity has disappeared.
The co-deposited amount of the organic polymer varies depending on the
concentration of the organic polymer, the stirring, and the charge of the
organic polymer. Therefore, during the plating, the amount of the organic
polymer that will be co-deposited in the deposit is controlled by
selecting the above factors, which can be easily carried out.
As ferromagnetic metal ions, one or more different types of ions comprising
cobalt ions, nickel ions, and iron ions are used, and they are supplied by
dissolving soluble salts such as sulfates, chlorides, or acetates of
cobalt, nickel or iron in an electroless plating bath. Cobalt ions are
used in a concentration in the range of 0.005 to 2 mol/l, preferably 0.01
to 0.2 mol/l. Nickel ions are used in a concentration in the range of
0.001 to 1.5 mol/l, preferably 0.05 to 0.20 mol/l. Iron ions are used in a
concentration in the range of 0.002 to 1 mol/l, preferably 0.01 to 0.15
mol/l.
As ferromagnetic metal ions used in the present invention, one or more of
Co, Ni and Fe is used as major component, but small amounts of ions of Mg,
Al, Ru, Si, Ti, V, Cr, Cu, Zn, Ga, Ge, Mo, Rh, Mn, Pd, Ag, Au, Pt, Sn, Te,
Ba, Ce, Pr, Sm, Re, W, Os, Pb, Bi, etc., may be contained, and these ions
may be supplied by adding their soluble salts. In the deposit, in addition
to these metals, sometimes, P, or B may be present depending on the type
of a reducing agent or a nonmetal such as C, N, 0, S, As, etc., may be
present depending on the type of an additive.
Although as a reducing agent for the metal ions, generally a hypophosphite
is used, a hydrazine salt, a borohydride or the like may also be used. The
reducing agent is used in the range of 0.01 to 1 mol/l.
As the complexing agent for the metal ions use is made of carboxylic acids
such as formic acid, acetic acid, propionic acid, butyric acid, glycolic
acid, lactic acid, oxalic acid, succinic acid, malonic acid, maleic acid,
itaconic acid, phthalic acid, malic acid, salicylic acid, tartaric acid,
tartronic acid, ascorbic acid, and citric acid, amino acids such as
glutamic acid, glycine, and asparaginic acid, weak acids such as gluconic
acid, and glutonic acid, or their salts, which may be used alone or in
combination. These complexing agents are used in a concentration in the
range of 0.02 to 1.5 mol/l, preferably 0.1 to 0.8 mol/l.
As a pH buffer, an ammonium salt, a carbonate, an organic acid salt is
used, and it is used in a concentration in the range of 0.01 to 2.5 mol/l.
As a pH adjuster, an alkali such as ammonia, and sodium hydroxide is used
to increase the pH and an acid such as sulfuric acid, and hydrochloric
acid is used to decrease the pH.
Usually, the plating solution that has not yet been made up without a pH
adjuster being added is between an approximately neutral solution and an
acid solution, and the pH is adjusted by adding the above hydroxide to
become alkaline. If the pH exceeds a prescribed value, an acid such as
hydrochloric acid, sulfuric acid, nitric acid, etc., is used.
The, the method of the production by physical vapor deposition is described
as follows.
The method of the present invention can be carried out by any of the
methods that are generally called physical vapor deposition processes
presented in known literatures. That is, any of the following processes
can be applied: the vacuum vapor deposition process wherein raw materials
for plating are vaporized under reduced pressure and are allowed to
condense on a substrate; the ion plating process wherein raw materials for
plating that have been vaporized are ionized under glow discharge to be
activated and allowed to deposit on a substrate; and the sputtering
process wherein glow discharge is effected in an inert gas atmosphere so
that raw materials for plating may be ionized and ejected by the
bombardment of the ionized gas and then may be attracted to a substrate to
be deposit thereon. The sputtering process includes the high-frequency or
direct current type magnetron sputtering system, the opposed target type
sputtering system, and the ion beam sputtering system, any of which may be
used. To make the organic polymer into a composite stably, the sputtering
process is preferable, and amongst others the high-frequency type
magnetron sputtering system, or the high-frequency opposed target type
sputtering system, or the ion beam sputtering system is most preferable.
The technique for depositing physically organic polymers is already known.
For instance, there are deposited films of polyethylene, sputtered films
of polytetrafluoroethylene or polyacrylonitrile, etc. However, these known
techniques are for forming a single film, and are not intended for the
prevention of corrosion as in the present invention. There is also a
report wherein electric characteristics concerning a deposited film of
copper and polyethylene are measured. The copper/polyethylene composite
film, in that report is unstable, the structure of the film is such that
the deposited metal takes the shape of islands cohered in the polymer, and
the report was directed only to the fact that the electric resistance
changes by annealing, so that the film in the report is different
substantially from the present magnetic recording thin film which is
highly resistant to corrosion.
There are also a report related to a method of producing a magnetic
recording medium (Japanese Patent Application Laid-Open No. 281120/1987)
wherein an organometallic monomer gas is introduced during vacuum
deposition of a ferromagnetic metal, and glow discharge treatment is
carried out so that an organic polymer is allowed to coexist at the
boundaries of columnar grains (between grains) of the segregated
ferromagnetic material, and a report related to the production of a
Co-Cr-polyethylene film wherein Co-Cr alloy and polyethylene are
simultaneously deposited.
However, in the former case, since an organic monomer gas is used, an
organic material segregates only at the grain boundaries (between grains),
and therefore the film structure is substantially different from that of
the present invention, so that an effect of improving corrosion resistance
at the level that will be attained by the present invention cannot be
secured. In the latter case, since an organic material segregates only at
the boundaries (between grains) probably due to violent decomposition of
polyethylene, and the magnetic properties such as the coercive force
lowers remarkably, the film cannot be used practically, as a magnetic
recording medium. As will be understood from the above description, if a
common organic polymer is used, it is liable to suffer the decomposition
during the physical vapor deposition, and probably due to the presence of
organic polymers whose molecular weights have been reduced by the
decomposition, the magnetic properties are greatly disturbed-particularly
the coercive force is lowered--, so that the film cannot be used in
practice as a magnetic recording medium.
In the present invention, attention is particularly directed to the
stability of an organic polymer to decomposition, and useful chemical
structures of organic polymers have been decided. That is, it has been
found that it is preferable to use, as polymers to be used in physical
vapor deposition, aromatic organic polymers having a weight-average
molecular weight of 1,000 to 5,000,000, and the selection of polar groups
having an effect of increasing the melting point and the selection of the
range of the molecular weight are also important.
The present invention is carried out under a pressure of 10.sup.-1 to
10.sup.-6 Torr. The optimum range of the pressure is determined from the
points of the vapor deposition process, the vapor deposition speed, the
level of the quality of the product, and the economy. That is, in the case
of ion plating or sputtering, the present invention is carried out under a
pressure of up to 10.sup.-1 Torr and between 10.sup.-2 and 10.sup.-3 Torr
where glow discharge will occur, and the gas to be introduced is nitrogen,
helium, argon, or the like. Nitrogen has such a defect that it is liable
to form nitrogen oxides during the discharge, and helium has such a defect
that it is weak in ionization force. In the present invention, argon is
most preferable. The pressure in the case of vacuum deposition is
10.sup.-2 to 10.sup.-6 Torr, preferably up to 10.sup.-4 Torr (i.e., in the
range of 10.sup.-4 to 10.sup.31 6 Torr). In the case of vacuum deposition,
a pressure of 10.sup.-4 Torr or higher makes the deposition speed too
slow, and makes the quality of the magnetic film poor, particularly the
adhesion to the substrate, and a pressure of 10.sup.-6 Torr or below makes
the practical operation line long, which is not economical. In the case of
ion plating and sputtering, it is carried out under a pressure of
10.sup.-2 to 10.sup.3 Torr where glow discharge will occur to provide a
magnetic film good in magnetic property.
As vapor sources, a metal and an organic polymer may be evaporated
separately or a composite vapor source may be used, obtained by mixing the
metal and the organic polymer in advance with each other as far as they
arc similar to each other in their evaporating temperature and vapor
pressure. As a heating source, a resistance heating process, an induction
heating process, an electron beam process, or a combination of these may
be used. As a crucible, in the case of the electron beam process, a
water-cooled copper crucible, ceramics, etc., can be used, and in the case
of other heating processes, a carbon boat, a tungsten boat, a tantalum
boat, and a ceramic boat can be used. In the case of the sputtering
process, sputtering is carried out using, as target, a composite target of
an organic polymer and a metal or a single organic polymer target and a
single metal target. In this case, in order to obviate that the
temperature rises, it is preferable that the target and the deposited
matrix are cooled if required. Although the evaporation speed varies
depending on the types of the metal and the organic polymer, the degree of
vacuum, and the heating temperature, there is not any particular
restriction on the evaporation speed in the present invention.
The magnetic film thickness is in the range of 0.005 to 5 .mu.m, and in the
case for high density recording, the magnetic film thickness is preferably
up to 0.2 .mu.m.
As a substrate on which the magnetic film will be formed, use is made of a
non-metallic substrate such as PET film (polyethylene terephthalate film),
polyimide film, a glass substrate, and a ceramic substrate that have been
activated suitably, and a metal substrate for example made of an Al alloy.
The recording medium according to the present invention has characteristic
effects given below under (1) to (4):
1) In a magnetic film an organic polymer is made into a composite in the
order of the molecules, thus due to the action of the co-deposited
polymer, local cells formed by corrosion are subject to the dispersion
effect and the electrical insulating effect, and the corrosion resistance
increases due to the oxygen barrier property and the corrosion prevention
property.
2) By the action of the organic polymer, the metal crystals are further
made minute, the crystal size is further made uniform, and the recording
medium is made smooth, so that the corrosion resistance is improved.
3) By the action of the water-soluble organic polymer, trapping of H.sub.2
gas in the deposit is suppressed, thereby making the film dense.
4) The amount of the water-soluble organic polymer that will be
co-deposited into the deposit matrix is determined by the molecular
weight, the basic skeleton, the type of the polar groups, the density of
the polar groups, and the content of the water-soluble organic polymer
that will be incorporated into the plating bath, and by the interaction of
the plating conditions. By said interaction, the diameter and the shape of
the deposited grains can be controlled, and particularly the molecular
weight, the type and the density of polar groups influence greatly the
corrosion resistance, and the diameter and the shape of the grains.
In the present invention, the composite material is formed from the
deposited metal and the polymer on a molecular level. This not only
contributes to a remarkable improvement in the corrosion resistance of the
deposited coating layer but also brings about an effect that no defects
causing an error of the recording medium is formed.
A magnetic film containing the organic polymer of the present invention
incorporated therein exhibits magnetic characteristics equal or superior
to those of the conventional plated magnetic film and further has
excellent corrosion resistance. For this reason, it is possible to
remarkably reduce the thickness of the protective layer commonly used in
the conventional recording medium while maintaining the reliability of the
recording medium.
This enables a reduction in the burden of the protective layer, so that the
process can be simplified. Further, since the distance between the head
and the magnetic film can be reduced, not only spacing loss can be
suppressed but also it becomes possible to cope with an increase in the
density. This effect is very advantageous from the industrial viewpoint.
EXAMPLES
The present invention is further described in more detail with reference to
the following Examples, but the present invention is not limited to the
Examples.
Pretreatment for Plating
In the case where PET film (having a thickness of 10 .mu.m) was used, the
PET film was etched with an aqueous solution of 75 g of NaOH solution in 1
liter of water at 60 .degree. C. for 5 to 15 min, and then was immersed in
an aqueous solution of 0.1 g of SnCl in 1 liter of water at 25.degree. C.
for 2 to 4 min, then in an aqueous solution of 0.1 g of AgNO.sub.3 at
25.degree. C. for 2 to 4 min, and then in an aqueous solution of 0.1 g of
PdCl.sub.2 at 25.degree. C. for 2 to 4 min to activate the PET surface. In
some cases, PET film on which Pd nuclei had been deposited by the
sputtering process was used (Lumine, a tradename of oray ndustries, Inc.).
In the case using an Al alloy substrate, a non-magnetic Ni-P layer was
deposited on the Al alloy surface, and then a magnetic deposit was formed
thereon.
The Plating Baths and the Plating Conditions
The water-soluble organic polymers used in the plating baths of the present
invention are shown in Table 1, comparative organic polymers are shown in
Table 2, and the basic plating bath compositions that were used are shown
in Table 3. The plating bath compositions of the present invention formed
by combining them are shown in Table 4.
The plating time was 190 sec, and a thickness of 800 to 1600 .ANG. was
obtained.
The Physical Vapor Deposition Conditions
i) Magnetron sputtering:
In a high-frequency magnetron sputtering apparatus, by using a Cr target
for the formation of a primary coat, and a Co--30 % Ni alloy target for a
recording layer or Co-40% Fe, Co-25% Pt alloy target, having a size of 3
inches, a primary Cr coat having a thickness of 5,000 A, and a recording
layer having a thickness of 600 A were formed. The sputtering conditions
of the recording layer were as follows: the preparatory evacuation:
3.times.10.sup.-6 Torr; the Ar gas pressure: mainly 5 m Torr; the output:
mainly 200 W; and the substrate temperature: room temperature. The organic
polymer was formed into cubic pellets (5 mm.times.5 mm.times.5 mm), and a
required number of the pellets were fixed on suitable positions of the
alloy target so that they might be used as a metalorganic polymer
composite target. A substrate of glass having a thickness of 90 mm was
used.
ii) The Opposed Target Type Sputtering:
An opposed target type sputtering apparatus was used with the plate
interval being 100 mm to form a film. Other conditions followed those of
the magnetron sputtering process.
iii) The Vacuum Deposition Process (of the Electron Beam Heating Type):
A vacuum deposition apparatus with an electron gun was used, crucibles for
a metal and for an organic polymer were set, and the metal and the organic
polymer were simultaneously deposited. As a metal vapor source, Co-15 wt.
% Ni was used. As a deposition base, a polyimide film was used, and each
film having a thickness of 1,000 .ANG. was formed under a pressure of
1.times.10.sup.-5 Torr.
iv) The Vacuum Deposition Process (of the Resistance Heating Type):
Each film was formed using the same conditions as those under iii), except
that vaporization was carried out using the resistance heating process.
Measurement of the Amount of Co-deposited Organic Polymers
Using a carbon-in-metal analyzing apparatus (EMIA-110 manufactured by
Horiba Ltd.), each sample was heated to 1,000.degree. to 1,350.degree. C.,
and the amount of the co-deposited organic polymer was measured
quantitatively by determining CO.sub.2 and CO released, or by using the UV
absorption technique, or the fluorescent X-ray technique (a 3371 model
manufactured by Rigakudenki: an analyzing crystal).
Analysis of the Metal Compositions
Analysis was carried out by the ICP process (a high-frequency plasma
analysis process; an ICAP-575 model manufactured by Nippon Jarrell Ash
Industries, Inc) or the fluorescent X-ray technique mentioned above.
Analysis of the Film Thicknesses
Each film was cut to form a ultrathin cut piece having the transversal
section of the film, and the thickness of the film was measured by a TEM
(a transmission type electron microscope; 2000FX manufactured by Nihon
Denshi Kabushiki-kaisha). Conversion was performed by taking the amount of
the co-deposited organic polymer into consideration from the total amount
of the metals found by the ICP process.
Measurement of magnetic characteristics
The coercive force (Hc), squareness ratio (Rs), saturation, and residual
magnetic flux densities (Br and Bs) were measured with a VSM (vibrating
sample magnetometer).
Corrosion resistance test
A shelf test was continuously conducted for 2 weeks in an environment of a
temperature of 60.degree. C. and a humidity of 90%, and the degree of
lowering in the saturation magnetic flux density,
##EQU1##
wherein B.sub.s is the saturation magnetic flux density immediately after
deposition and B.sub.s.sbsb.o is one after the test}, caused between the
state before test and the one after the test was determined with a VSM.
The corrosion resistance was graded based on the value of R as follows.
A: an R value of less than 2%
B: an R value of less than 4%
C: an R value of less than 8%
D: an R value of less than 16%
E: an R value of at least 16%
TABLE 1
__________________________________________________________________________
No.
Compound
##STR43##
(per 500 of mol. wt.)Polar group
__________________________________________________________________________
density
1 sodium salt of sulfonated novolak resin
ca 1,200
sulfone gp. 3.8
2 sodium salt of m-cresolmethylenesulfonic
ca 1,500
sulfone gp. 3
acid-formalin condensate
3 condensate of formalin with sodium m-cresol-
ca 3,000
sulfone gp. 2
bakelite-methylenesulfonate and Schaeffer's acid
4 condensate of formalin with sodium dihydroxy-
ca 3,000
sulfone gp. 1.8
naphthalenesulfonate
5 sodium salt of sulfonated polytannic acid
ca 20,000
sulfone gp. 2
6 condensate of formalin with sodium phenyl
ca 6,000
sulfone gp. 3.4
phenoldisulfonate
7 condensate of formalin with sodium naphthol-
ca 2,800
sulfone gp. 2.2
sulfonate and phenolsulfonic acid
8 condensate of formalin with phenanthrene
ca 3,200
sulfone gp. 1.3
and sodium phenolsulfonate
9 sodium salt of sulfonated poly-p-
ca 20,000
sulfone gp. 2
hydroxyvinylpyridine
10 ammonium sulfonate of nitrohumic acid
ca 10,000
sulfone gp. 1.2
carboxyl gp. 1
11 sodium ligninsulfonate (1)
ca 10,000
sulfone gp. 1.1
12 sodium ligninsulfonate (2)
ca 3,600
sulfone gp. 1.3
13 Cr chelate of sodium ligninsulfonate
ca 5,000
sulfone gp. 1.3
14 ammonium ligninsulfonate
ca 2,000
sulfone gp. 1.4
15 aminomethylated novolak resin
ca 1,400
amino gp. 3.8
16 aminomethylated condensate of
ca 2,500
amino gp. 3.4
formalin with naphthol
17 aminomethylated condensate of formalin with
ca 3,000
amino gp. 2.0
phenanthrene and phenol
18 sodium salt of sulfonated condensate of formalin
ca 3,000
sulfone gp. 3.0
with phenylphosphonic acid and phenol
phosphate gp. 1.0
19 aminomethylated condensate of formalin with
ca 3,500
sulfone gp. 1.6
sodium naphtholsulfonate amino gp. 1.3
20 condensate of formalin with naphthol and
ca 3,000
sulfone gp. 0.3
phenolsulfonic acid
21 ammonium sulfonate of nitrohumic acid
ca 9,000
sulfone gp. 0.1
carboxyl gp. 0.6
22 sodium ligninsulfonate (3)
ca 3,600
sulfone gp. 0.3
23 aminomethylated condensate of
ca 2,500
amino gp. 0.2
formalin with naphthol
__________________________________________________________________________
No.
Structure of hydroxystyrene polymer
##STR44##
__________________________________________________________________________
24
##STR45## 2,380
25
##STR46## 7,900
26
##STR47## 15,300
27
##STR48## 11,900
28
##STR49## 4,450
29
##STR50## 23,880
30
##STR51## 3,860
31
##STR52## 4,070
32
##STR53## 3,490
33
##STR54## 2,600
34
##STR55## 2,400
35
##STR56## 17,000
36
##STR57## 3,200
37
##STR58## 8,800
38
##STR59## 20,060
39
##STR60## 2,810
40
##STR61## 11,000
41
##STR62## 25,000
42
##STR63## 3,740
43
##STR64## 37,500
44
##STR65## 4,210
45
##STR66## 2,760
46
##STR67## 6,210
47
##STR68## 23,600
48
##STR69## 14,500
49
##STR70## 8,800
50
##STR71## 7,650
51
##STR72## 13,500
52
##STR73## 4,500
53
##STR74## 6,700
__________________________________________________________________________
compound molecular weight
__________________________________________________________________________
54 poly-p-hydroxy-vinylpyridine
20,000
55 formalin condensate of dihydroxynaphthalene
2,500
56
##STR75## 2,000
57
##STR76##
58
##STR77## 55,000
59
##STR78##
60
##STR79##
61
##STR80## 10,000
62
##STR81##
__________________________________________________________________________
TABLE 2
______________________________________
Symbol
Compound
##STR82##
of mol. wt.)density (per 500polar
______________________________________
group
Ra polyethylene glycol
ca 1,700
Rb sodium ligninsulfonate
ca 700 sulfone group 0.2
Rc gelatin ca 60,000
Rd polyethylene ca 100,000
Re polypropylene ca 200,000
______________________________________
TABLE 3
__________________________________________________________________________
Plating
bath Symbol
Bath composition
__________________________________________________________________________
Co--P A cobalt acetate (Co(CH.sub.3 COO).sub.2.4H.sub.2 O)
0.05 mol/l
Rochelle salt (KNaC.sub.4 H.sub.4 O.sub.6.4H.sub.2 O)
0.5 mol/l
ammonium acetate (CH.sub.3 COONH.sub.4)
0.5 mol/l
sodium hypophosphite (NaH.sub.2 PO.sub.2.H.sub.2 O)
0.2 mol/l
pH (ammonia liq.) 9.5.about.9.8
bath temp. 60.about.70.degree. C.
Co--P B cobalt chloride (CoCl.sub.2.6H.sub.2 O)
0.05 mol/l
sodium tartrate (NaC.sub.2 H.sub.4 O.sub.6.2H.sub.2
0.5 mol/l
ammonium chloride (NH.sub.4 Cl)
0.15 mol/l
sodium hypophosphite (NaH.sub.2 PO.sub.2.H.sub.2 O)
0.5 mol/l
pH (ammonia liq.) 9.5.about.9.8
bath temp. 75.about.85.degree. C.
Co--Ni--P
C cobalt sulfate (CoSO.sub.4.7H.sub.2 O)
0.06 mol/l
nickel sulfate (NiSO.sub.4.6H.sub.2 O)
0.04 mol/l
sodium citrate (Na.sub.3 C.sub.6 H.sub.5 O.sub.7.2H.sub.2
O) 0.3 mol/l
citric acid (C.sub.6 H.sub.8 O.sub.7)
0.25 mol/l
ammonium sulfate ((NH.sub.4).sub.2 SO.sub.
0.3 mol/l
sodium hypophosphite (NaH.sub.2 PO.sub.2.H.sub.2 O)
0.2 mol/l
pH (ammonia liq.) 8.about.8.5
bath temp. 75.about.85.degree. C.
Co--Mn--P
D cobalt sulfate (CoSO.sub.4.7H.sub.2 O)
0.06 mol/l
nickel sulfate (NiSO.sub.4.6H.sub.2 O)
0.04 mol/l
manganese sulfate (MnSO.sub.4)
0.03 mol/l
sodium tartrate (Na.sub.2 C.sub.4 H.sub.4 O.sub.6)
0.5 mol/l
ammonium sulfate ((NH.sub.4).sub.2 SO.sub.4)
0.5 mol/l
sodium hypophosphite (NaH.sub.2 PO.sub.2.H.sub.2 O)
0.2 mol/l
pH 9.0.about.9.4
bath temp. 75.about.85.degree. C.
Co--Ni--Re--P
E cobalt sulfate (CoSO.sub.4.7H.sub.2 O)
0.06 mol/l
nickel sulfate (NiSO.sub.4.6H.sub.2 O)
0.04 mol/l
ammonium perrhenate (NH.sub.4 ReO.sub.4)
0.007 mol/l
ammonium sulfate ((NH.sub.4).sub.2 SO.sub.4)
0.5 mol/l
sodium tartrate (Na.sub.2 C.sub.4 H.sub.4 O.sub.6)
0.5 mol/l
sodium hypophosphite (NaH.sub.2 PO.sub.2.H.sub.2 O)
0.2 mol/l
pH 8.5.about.9.5
bath temp. 75.about.80.degree. C.
__________________________________________________________________________
TABLE 4
__________________________________________________________________________
Plating conditions
Polymer added
Plating
Cpd. Plating base
Corrosion
No.
bath
No.
Amount (g/l)
material resistance
__________________________________________________________________________
Product
1 A 1 0.05 PET C
of 2 " 4 0.1 " A
present
3 " 7 0.2 " A
invention
4 " 10 1 " A
5 " 13 2 " B
6 " 16 0.2 " B
7 " 19 " " A
8 " 22 " " A
9 " 25 10 " A
10 " 28 0.5 " A
11 " 31 " " A
12 " 34 " " B
13 " 37 " " A
14 " 40 " " B
15 " 43 " " A
16 A 46 " PET (Lumirror)
B
17 " 49 " " B
18 " 52 " " B
19 B 2 0.05 PET C
20 " 5 0.1 " A
21 " 8 0.2 " A
22 " 11 1 " A
23 " 14 2 " B
24 " 17 20 " A
25 " 20 2 " B
26 " 23 5 " B
27 " 26 0.2 " A
28 " 29 0.5 " A
29 " 32 0.2 " A
30 " 35 1 " A
31 B 38 0.2 PET B
32 " 41 0.5 " B
33 " 44 0.5 " A
34 " 47 0.5 PET (Lumirror)
A
35 " 50 0.2 " A
36 " 53 2 " A
37 C 3 0.05 PET film C
38 " 6
0.1 " B
39 " 9 0.2 " A
40 " 12 1 " A
41 " 15 0.5 " B
42 " 18 0.2 " A
43 " 21 0.5 " A
44 " 24 10 " B
45 " 27 2 " A
46 C 30 1 PET film A
47 " 33 0.5 " A
48 " 34 0.2 " A
49 " 37 0.5 " A
50 " 40 1 " B
51 " 43 0.5 PET (Lumirror)
A
52 " 46 0.2 " B
53 " 49 1 " B
54 D 6 0.2 PET film A
55 " 26 0.5 " A
56 " 29 0.5 " A
57 " 33 0.5 " A
58 " 43 2 " A
59 E 10 0.2 PET film A
60 " 27 0.5 " A
61 E 28 0.5 PET film A
62 " 31 0.5 " A
63 " 48 2 " A
Comparative
64 A -- -- PET film D
product
65 B -- -- " D
66 C -- -- " D
67 D -- -- " D
68 E -- -- " D
69 A 6 0.001 " D
70 A Ra 2 " E
71 C Rb 2 " E
72 C Rc 2 " E
__________________________________________________________________________
TABLE 5
__________________________________________________________________________
Amount of co-
Physical deposition
Metal Polymer used
Base for deposited
Corrosion
No. process target
No. deposition
polymer (wt.
resistance
__________________________________________________________________________
According to the
present invention
73 Magnetron sputtering process
Co--Ni
4 Glass B
74 " " 7 " B
75 " " 25 " 0.01 B
76 " " 25 " 0.2 A
77 " " 25 " 1.3 A
78 " " 25 " 4.7 B
79 " " 29 " A
80 " " 31 " A
81 " " 37 " A
82 " " 39 " A
83 " " 41 " A
84 " " 43 " A
85 " " 46 " A
86 " " 48 " A
87 " " 54 " B
88 " " 55 " A
89 " " 56 " B
90 " " 57 " A
91 " " 58 " A
92 " " 59 " B
93 Magnetron sputtering process
Co--Ni
60 Glass A
94 " " 61 " A
95 " " 62 " A
96 Opposed target type
" 25 " A
sputtering process
97 Opposed target type
" 29 " A
sputtering process
98 Opposed target type
" 61 " A
sputtering process
99 Opposed target type
" 62 " A
sputtering process
100 Electron beam heating type
" 25 Polyimide film B
vacuum deposition process
101 Electron beam heating type
" 29 " B
vacuum deposition process
102 Electron beam heating type
" 61 " B
vacuum deposition process
103 Electron beam heating type
" 62 " A
vacuum deposition process
104 Magnetron sputtering process
Co--Ni
-- Glass E
105 Opposed target type
" -- " E
sputtering process
106 Electron beam heating type
" -- Polyimide film E
vacuum deposition process
107 Electron beam heating type
" Rd " 1.3 E
vacuum deposition process
108 Electron beam heating type
" Re " 1.1 E
vacuum deposition process
109 Resistance heating type
" Rd " 1.7 E
vacuum deposition process
110 Resistance heating type
" Re " 1.3 E
vacuum deposition process
__________________________________________________________________________
The corrosion resistance of the magnetic plated coatings prepared by the
electroless plating process according to the present invention is shown in
Table 4 in comparison with the corrosion resistance of the comparative
products. Hc shows a coercive force and Rs shows a squareness ratio.
The magnetic characteristics of the magnetic plating coatings of Ex. Nos. 1
to 36 wherein plating baths A and B were used as a base bath were Hc of
700 to 1200 Oe and Rs of 0.6 to 0.8. The magnetic characteristics of the
magnetic plating coatings of Ex. Nos. 54 to 58 wherein plating bath D was
used were Hc of 500 to 900 Oe and Rs of 0.65 to 0.75. The magnetic
characteristics of the magnetic plating coatings of Ex. Nos. 59 to 63
wherein plating bath E was used were Hc of 700 to 1100 Oe and Rs of 0.6 to
0.8.
The results of the corrosion resistance substantiate that the corrosion
resistance of product Nos. 1 to 63 of the present invention is remarkably
superior to that of the comparative product Nos. 64 to 72.
It is apparent that the magnetic coatings (Nos. 70 to 72) prepared by
making use of baths each containing a water-soluble organic polymer not
meeting the requirements of the present invention have lowered corrosion
resistance.
Table 5 shows the corrosion resistance of the magnetic films obtained by
the physical vapor deposition method according to the present invention
and the conversion resistance of the comparative products.
The magnetic films Nos. 73 to 103 according to the present invention showed
such magnetic properties that Hc =500 to 1,000 Oe, and Rs =0.6 to 0.8,
which were almost the same as those of the comparative magnetic films Nos.
104 to 107 wherein Hc =500 to 1,100 Oe, and Rs=0.6 to 0.8. Remarkable
lowering of the magnetic properties due to the presence of the organic
polymers that were made into composites was not observed.
The test results of the corrosion resistance show that the corrosion
resistance of the magnetic film Nos. 73 to 103 according to the present
invention is more excellent than that of the comparative magnetic film
Nos. 104 to 109.
The Hc of the magnetic films (Nos. 106 to 109) wherein common organic
polymers were made into composites that did not meet the conditions of the
present invention was 50 to 100 Oe, which was remarkably low. From Table
5, it can be understood that corrosion resistance was not improved.
Similar results were obtained in the case of Fe-Co type, Fe-Ni type, and
Co-Pt type magnetic films.
As seen in the description, both processes of the invention, the
electroless plating and the physical vapor deposition, can provide a
resulting recording medium with an unexpectedly improved resistance to
corrosion.
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